− All the identified major factors influence decommissioning strategies to a greater or lesser extent. The selection of a decommissioning strategy needs to be based on the evaluation of all relevant factors. Techniques may be used such as multi-attribute analyses that would consider all the relevant factors, constraints and conditions, their interactions and weights to select the appropriate strategy. Other conditions and constraints may exist, which are not dealt with in this report, and are important to include in site specific evaluations.
− The constraints associated with funds, the waste management system and human resources could limit the strategies for decommissioning to deferred dismantling independent of other factors. If this is the case, decommissioning strategies that are not necessarily ‘good practices’ may be forced.
− Deferred dismantling caused by the above-mentioned overwhelming constraints is generally attributable to lack of decommissioning planning which is in turn due to insufficient legal or regulatory framework. Authorization of facilities that use radioactive material needs to include decommissioning considerations from the design phase to operational and shut down phases.
− When the forced decommissioning strategy is deferred dismantling, the problems associated with decommissioning are only delayed and in some cases exacerbated.
− Legal and regulatory infrastructures related to decommissioning need to be established as soon as practicable.
− When constraints occur, management has to proactively take steps to remove the constraints or, if that is not possible, to eliminate or minimize their impacts.
If deferred dismantling is forced due to overwhelming constraints, active retrospective activities are required to cover such items as:
− Essential actions in the transition period to render the facility ‘safe’ for the extended storage period;
− Management of the deferred dismantling phase;
− Interim management of waste and spent fuel;
− Updating and preservation of the facility history and technical information on radiological surveillance, design and operation;
− Programmes to ensure planning and execution of final decommissioning.
REFERENCES
[1] REISENWEAVER, D.W., The International Atomic Energy Decommissioning Concept, Proc. of an Int. Conf. on Safe Decommissioning for Nuclear Activities, Berlin, 14–18 Oct. 2002, IAEA, Vienna (2003) 123–130.
[2] INTERNATIONAL ATOMIC ENERGY AGENCY, Application of the Concepts of Exclusion, Exemption and Clearance, Safety Standards Series No. RS-G-1.7, IAEA, Vienna (2004).
[3] LOUGH, W.T., JOHNSON, W.R., WHITE, K.P., A Multi-Criteria Decision Aid for Evaluating Nuclear Power Plant Decommissioning, Proc. of an Int. Decommissioning Symposium, Pittsburgh (1987) 314–323. .
[4] RAHMAN, A., Multi-attribute Utility Analysis — a Major Decision Aid Technique, Nuclear Energy, 42, No 2, April, 87–3 (2003).
[5] INTERNATIONAL ATOMIC ENERGY AGENCY, Decommissioning of Nuclear Power Plants and Research Reactors, IAEA Safety Standards Series No. WS-G-2.1, IAEA, Vienna (1999).
[6] INTERNATIONAL ATOMIC ENERGY AGENCY, Decommissioning of Medical, Industrial and Research Facilities, IAEA Safety Standards Series No. WS-G-2.2, IAEA, Vienna (1999).
[7] INTERNATIONAL ATOMIC ENERGY AGENCY, Decommissioning of Fuel Cycle Facilities, Safety Standards Series No. WS-G-2.4, IAEA, Vienna (2001).
[8] INTERNATIONAL ATOMIC ENERGY AGENCY, Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management, GOV/INF/821-GC941)/INF/12, 22 Sept., IAEA, Vienna (1997).
[9] INTERNATIONAL ATOMIC ENERGY AGENCY, On-site Disposal as a Decommissioning Strategy, IAEA-TECDOC-1124, IAEA, Vienna (1999).
[10] INTERNATIONAL ATOMIC ENERGY AGENCY, Financial Aspects of Decommissioning, IAEA-TECDOC-1476, IAEA, Vienna (2005).
[11] LARAIA, M., “IAEA Views on issues, trends, and development in decommissioning of nuclear facilities and Member States’ experience”, Proc. Int. Conf. Nuclear Decommissioning 2001, IMECHE Conference Transactions 2001-8, Professional Engineering Publishing Ltd, London (2001) 345–354.
APPENDIX I.
EXAMPLES OF PRACTICAL EXPERIENCE I.1. INTRODUCTION
In practice it is often found that a decommissioning strategy for a particular facility has to be selected in the context of a very complex set of influencing factors — as discussed in this report. Furthermore, the nature of this complexity tends to evolve with time, such that adjustments have to be made to the selected strategy or to important aspects of its implementation.
In many cases, the basic lesson learned is that if the initial strategy has been well chosen (taking comprehensive account of all relevant issues), then it can be adapted to deal with changing circumstances. Sometimes, it has even been possible to adapt a strategy to deal with a potentially severe constraint.
The following examples are set out as case studies, enabling the reader to appreciate the overall context in which the decommissioning strategy was selected and to understand why particular measures were taken when implementing the strategy. Key aspects from these case studies are summarized below.
I.2. DECOMMISSIONING STRATEGIES FOR THE KOREAN RESEARCH REACTORS KRR-1 AND KRR-2
The initial pressure was for immediate dismantling (the reactor site had already been sold for other uses). Then it became apparent that the problem of sanctioning a national waste repository was not likely to be resolved in the short term, so it seemed that the strategy would have to be changed to deferred dismantling (safe enclosure). This approach also allowed time for the development of some necessary technologies.
Some time after the decommissioning project had commenced (based on deferral), an operational date for a waste repository was established. This created an opportunity to revise the decommissioning strategy further, leading to a way forward that was somewhere between immediate and deferred dismantling.
The solution was to adopt a compromise time frame (2008) for the completion of the decommissioning project. This compromise offered the possibility of completion in the shortest practicable time consistent with the need to reuse the site, the expected earliest availability of a waste repository and the need to ensure that enough time was still available for the required technology developments. In addition, the project team had to deal with a lack of facility history and records, together with a lack of staff having experience operating these reactors.
I.2.1. Introduction I.2.1.1. Site
Both Korean research reactors #1 and #2 are located at Gongnung-dong, Seoul. The site was formerly used by the Korea Atomic Energy Research Institute (KAERI) before it was sold to the Korea Electric Power Corporation (KEPCO). The total area of the site is 48 000 m2 and the buildings occupy 7800 m2.
I.2.1.2. Main characteristics of the reactors
The construction of the first research reactor, Korean Research Reactor #1 (KRR-1) was started in July 1959 and the reactor became critical on March 19, 1962. The KRR-1 was a TRIGA Mark II type and had an open pool and a fixed core. The reactor was utilized for the education and training of the students of nuclear engineering and basic tests on nuclear characteristics. It had been operated for 36 000 hours until it was shut down on January 1995.
The total energy generation during the operation was 3700 MWh and the maximum neutron flux was 1x1013 n/cm2 sec. The fuel was 20% enriched uranium in a chemical form of Zr-UH.
Korean Research Reactor #2 (KRR-2) came into operation in 1972 and enabled research on nuclear characteristics, radioisotope production and production of labeled compounds for medical applications. It generated a total energy of 69 000 MWh during the 55 000 hours operation till it was shut down in 1995 at the same time as KRR-1. It was a TRIGA MARK-III type with an open pool and a movable core. The fuel was 70 % enriched uranium in a chemical form of Zr-UH. Water was used as a moderator, coolant and reflector, (whereas graphite was used as a reflector for KRR-1).
I.2.2. Decommissioning projects
I.2.2.1. Reasons for decommissioning
In 1996, it was concluded that KRR-1 and KKR-2 would be shut down and dismantled. The main reason for decommissioning was that the condition of the facilities had deteriorated and the relevant regulations had become stricter. The surrounding areas became urbanized and the number of inhabitants had rapidly increased near the reactor site. Furthermore, high cost was expected for the modification and restart of the operation. Another reason was the start of the operation of a new research reactor, HANARO, which is located at the Daejeon site. It was expected that the new reactor could satisfy all the domestic needs of research reactor utilization in Korea for a long time.
I.2.2.2. Decommissioning plan
A project was launched for the decommissioning of the reactors in January 1997 with the goal of completion by 2008. The project was divided into 5 steps namely:
(1) Preparation (Jan. 1997–Dec. 2000): establishment of the decommissioning strategies, engineering, preparation of detailed procedures, and licensing;
(2) Dismantling of the auxiliary facilities of the KRR-2 (Jan. 2001–Dec. 2002): dismantling the laboratories, lead hot cells and concrete hot cells of the KRR-2;
(3) Dismantling of the reactor hall of the KRR-2 (Jan. 2003–Dec. 2004): dismantling of the internals in the pool including the core, and bio-shielding concrete;
(4) Dismantling of the KRR-1 (Jan. 2005–Dec. 2007);
(5) Final evaluation of the residual radioactivity and de-licensing (2008).
I.2.2.3. Strategies for decommissioning
The following strategies were decided upon at the beginning of the preparation phase:
(1) Dismantling time: immediately after the licensing;
(2) Final state of the site: clearance of the site and buildings after the removal of all the radioactive material;
(3) Waste: minimization of the radioactive waste, which will be packed into 200-liter drums and 4 m3 containers and temporarily stored at the site until transportation to the national repository facility in 2008;
(4) Technologies: development of the technologies directly required for the dismantling of the KRR-1 and -2 during the project, and for any future demands in connection with the project;
(5) Preparation of the next projects: participation of private companies for a joint development and technology transfer.
I.2.3. Factors influencing the strategic decision
I.2.3.1. Legal conditions
Under the Atomic Energy Act (concerning the decommissioning of power reactors and related facilities) and the Enforcement Regulations (concerning the application for approval of the decommissioning), the licensee for an operation, with an intention to decommission a power reactor, should submit a decommissioning plan and obtain approval from the Ministry of Science and Technology (MOST). The provisions for the decommissioning of power reactors were extended to research reactors.
The Act also determined that a decommissioning plan should include the following:
(1) Methods for the dismantling of power reactors and associated facilities, and a work schedule;
(2) Methods for the removal of the radioactive material and for decontamination;
(3) Radioactive waste treatment and disposal;
(4) Necessary counter measures against radioactive hazards;
(5) Assessment of the environmental impacts and the measures for their minimization;
(6) Quality assurance programme.
Detailed standards and guidance were not defined in the Act and its Enforcement Regulations, but internal guidance from the Korea Institute of Nuclear Safety (KINS) was issued for the safety evaluation of the decommissioning plans of the research reactors and fuel cycle facilities. The Act and the internal guidance from the KINS defined only the procedures and safety requirements, not the criteria or the methods for the selection of the decommissioning strategies. The implementer was expected to choose the optimum strategy and technologies,
and ensure safety of the selected strategy. This means that the legal system does not have any influence on the selection of the strategies for the decommissioning of the research reactors.
I.2.3.2. Funding
The Korean Research Reactors #1 and #2 were constructed and operated by KAERI, funded by the Korea government. The government provided all the financial resources for the construction and operation of the research reactors. KAERI obtained approval on a master plan from the MOST and started a project for the decommissioning of the research reactors.
According to the project plan, the government guaranteed all the decommissioning funds, including waste disposal and research and development. This financial support was also expected if deferred dismantling was selected. Thus funding was not an important factor in the selection of the decommissioning strategies.
I.2.3.3. Waste management system
The total amount of the radioactive waste, to be generated during the decommissioning of the research reactors was estimated at 168 m3 from the KRR-1 and 453 m3 from the KRR-2. The radioactive material could be classified into activated material and those contaminated by
60Co and 137Cs. All the spent fuel was returned to the United States, the country of origin.
Most of the contaminated material was expected to be decontaminated by chemical or physical-chemical methods to clearance levels.
At the initial stage of strategy development and before the commencement of detailed engineering, all the waste management systems, including the storage facilities, were moved to the Daejeon site from the Seoul site where the reactors were located. The transportation of the radioactive waste to the Daejeon site required funding. By law, public consultation was not required since the Daejeon site is an institute and not a waste repository. Since the plan for the construction of a repository facility by the Korea Hydraulic and Nuclear Power Company (KHNP) was not clear at that time, a deferred dismantling strategy seemed the preferred strategy. The research reactors could be safely enclosed for several years until the plan for disposal of the waste could be established. The target date of 2008 for an operational waste repository was established after the decommissioning project commenced.
I.2.3.4. Reuse of the site and buildings
The site on which the reactors operated was already sold in 1985 to KEPCO. The section of the site and facilities of the research reactors were leased to the KAERI. A contract required that the site be returned as soon as possible after decommissioning and the removal of all the radioactive material. KEPCO planned to use the entire site as a training centre for its staff and had already started to use the remainder of site before the commencement of the decommissioning project. Under these conditions an immediate dismantling strategy seemed essential. The transfer of all the radioactive waste was not possible before 2007 and the project was prolonged for the development of the technologies for decommissioning and the minimization of radioactive waste. The target date of 2008 was finalized for the completion of the decommissioning project and the return of the site.
I.2.3.5. Local economy and social issues
The research reactors were located in Seoul, whose economic scale was too large to be influenced by the decommissioning project of small research reactors. The annual budget for
development budget of KAERI. KAERI had the funds to perform the decommissioning project. The project was not expected to impact significantly on the local economy. Funding was therefore not a factor in the selection of a decommissioning strategy.
According to the KEPCO plan, many trainees whose qualifications were not nuclear science and/or engineering were expected around the decommissioning site. The surrounding areas also became urbanized with high population density. Generally Koreans are opposed to nuclear facilities close to their houses, especially if they appear to be in an uncontrolled state.
The strategy of deferred dismantling was expected to be less acceptable to the inhabitants around the site than immediate dismantling even if stretched over a somewhat longer period.
I.2.3.6. Human resources
Even though the same worldwide trend of a decreasing number of students in the nuclear engineering departments of universities had also appeared in Korea, the nuclear industries remained proactive. It was expected that more than 23 nuclear power plants would be operated in the near future in Korea and nuclear fuel cycle facilities such as fuel fabrication plants would continue their operations according to the nuclear power production. Research and development in nuclear science was also stipulated by a long and medium term plan, funded by the government at a fraction of the electricity fee. Thus a lack of suitably qualified human resources was not expected in the future, especially during the decommissioning of the research reactors and even in the case of deferred dismantling for several tens of years.
After the shut down of the KRR-1 and -2, most of the operational staff of the reactors and the auxiliary facilities such as the hot cells, moved to the Daejeon site for the operation of the new research reactor and some of them retired. No staff with experience in the reactor operations were part of the decommissioning project team except for some retired manpower that were utilized on a contract basis.
A major problem was the lack of facility history and records. For example, there were many items with a high radioactivity in the concrete hot cells, but there were no records of them.
Before dismantling, each item in the hot cells had to be identified and operational experience helped to reduce the cost and time required for the identification. For deferred dismantling, detailed documents on the status of the facilities are to be prepared on the basis of the operator’s experience and preserved for later dismantling. This preparation of the documents would require additional funding.
I.2.3.7. Others
In 1997 when the decommissioning project of the research reactors was started, there was no expertise, technologies and experience on decommissioning in Korea. The options for the execution of the project were to use a foreign company with its technologies or to develop technologies within KAERI. It was decided that in house development of technologies would be desirable to prepare for future decommissioning of the many research facilities, fuel manufacturing facilities, power reactors and small facilities for medical uses at KAERI.
A timely supply of the necessary technologies seemed to furnish a key for the success of the project. Many technologies were required even at the planning stage for which limited development time existed. A longer transition period was required to allow for the development of the required technology.
I.2.4. Decision on the strategies
Some major factors that impacted on the selection of a decommissioning strategy and planning are summarized in the table below and discussed from the viewpoint of their strengths and weaknesses. The factors are considered for three categories namely; immediate and deferred dismantling and no influence. Generally it seems that the funding and waste management systems are the most important factors, because in the case of no funding and/or no waste management system, an immediate dismantling strategy is not possible. But for KRR-1 and KRR-2, immediate dismantling was selected because the return of the site was very urgent, deferred dismantling was expected to be difficult from a public acceptance perspective and a national repository facility was expected in the near future (Table A-1).
The selection of the immediate dismantling for KRR -1 and -2 meant that the negative impacts from the lack of a waste management system and the required technologies had to be considered and managed.
Table A-1. Influence of factors on decommissioning strategies for Korean reactors Factors Immediate
dismantling Deferred
dismantling No influence
Legal conditions X
Funding X
Waste management systems X
Reuse of site and buildings X Local economy/social issues X
Human resources X
Local technology/expertise X
For the decommissioning of the KRR -1 and -2, a new waste management system, including classification, decontamination, packing and temporary storage, was established by considering the following requirements.
• Treatment of all the liquid waste by a membrane process and solar evaporation since no discharge of liquid waste was legally possible at the reactor site;
• Decontamination of the solid waste as far as possible by the equipment and technologies developed;
• Classification, storage and packing of the wastes according to their activities and their properties.;
• Temporary storage of the radioactive waste in the reactor hall of the KRR #2 after being packed in 200-litre drums and 4m3 containers until transportation to the national repository facility is possible.
A foreign company was contracted for the development of technologies required at an early stage of planning of the decommissioning project. It was however decided that the technologies required for the decommissioning of the hot cells and reactors would be developed in house. The lack of the technologies can be overcome, but the decommissioning
A foreign company was contracted for the development of technologies required at an early stage of planning of the decommissioning project. It was however decided that the technologies required for the decommissioning of the hot cells and reactors would be developed in house. The lack of the technologies can be overcome, but the decommissioning